drug-discovery-prompts/upstream/K-Dense-AI-scientific-agent-skills/skills/database-lookup/references/sdss.md

title, task, lineage_type, upstream_source, upstream_sha, imported_at, prompt_class, upstream_changes, author, validated

title	task	lineage_type	upstream_source	upstream_sha	imported_at	prompt_class	upstream_changes	author	validated
SDSS SkyServer API		import	https://github.com/K-Dense-AI/scientific-agent-skills/blob/9c9bd2e9/skills/database-lookup/references/sdss.md	9c9bd2e9	2026-06-26	prompt	accepted	upstream	false

SDSS SkyServer API

Base URL

https://skyserver.sdss.org/dr18/SkyServerWS

Replace dr18 with the desired data release (e.g., dr17, dr16).

Authentication

No API key required. All endpoints are public.

Key Endpoints

1. SQL Search (CasJobs-style free-form SQL)

GET /SearchTools/SqlSearch

Parameter	Type	Description
cmd	string	Required. SQL query against SDSS CasJobs schema.
format	string	json, xml, csv, html, votable. Default: html.

Example — query 10 galaxies:

https://skyserver.sdss.org/dr18/SkyServerWS/SearchTools/SqlSearch?cmd=SELECT TOP 10 objid,ra,dec,u,g,r,i,z FROM PhotoObj WHERE type=3&format=json

Type codes: 3 = galaxy, 6 = star.

Response (JSON):

[
  {"Rows": [
    {"objid": 1237645941825863680, "ra": 195.123, "dec": 2.456, "u": 22.1, "g": 20.8, "r": 19.5, "i": 19.1, "z": 18.9}
  ]}
]

2. Radial Search

GET /SearchTools/RadialSearch

Parameter	Type	Description
ra	float	Required. Right ascension (degrees).
dec	float	Required. Declination (degrees).
radius	float	Search radius in arcminutes. Default: 1.
format	string	json, xml, csv.
limit	int	Max results.
objtype	string	Filter: star, galaxy, or blank for all.

Example — objects within 2 arcmin of RA=180, Dec=+0.5:

https://skyserver.sdss.org/dr18/SkyServerWS/SearchTools/RadialSearch?ra=180&dec=0.5&radius=2&format=json&limit=10

3. Rectangular Search

GET /SearchTools/RectangularSearch

Parameter	Type	Description
min_ra	float	Minimum RA (degrees).
max_ra	float	Maximum RA (degrees).
min_dec	float	Minimum Dec (degrees).
max_dec	float	Maximum Dec (degrees).
format	string	json, xml, csv.
limit	int	Max results.

4. Object Lookup by ObjID

GET /SearchTools/SqlSearch?cmd=SELECT * FROM PhotoObj WHERE objid={objid}&format=json

5. Spectra Search by Plate-MJD-Fiber

GET /SearchTools/SqlSearch?cmd=SELECT * FROM SpecObj WHERE plate={plate} AND mjd={mjd} AND fiberid={fiberid}&format=json

6. Image Cutout Service

GET /ImgCutout/getjpeg

Parameter	Type	Description
ra	float	Required. RA (degrees).
dec	float	Required. Dec (degrees).
scale	float	Arcsec/pixel. Default: 0.396127.
width	int	Image width in pixels. Default: 512.
height	int	Image height in pixels. Default: 512.

Example:

https://skyserver.sdss.org/dr18/SkyServerWS/ImgCutout/getjpeg?ra=180.0&dec=0.5&scale=0.4&width=256&height=256

Returns JPEG image data.

7. Spectrum Plot/Data

Spectrum FITS files can be retrieved from the Science Archive Server:

https://data.sdss.org/sas/dr18/spectro/sdss/redux/{run2d}/spectra/{plate}/spec-{plate}-{mjd}-{fiberid}.fits

Important SQL Tables

Table	Description
PhotoObj	Photometric measurements (positions, magnitudes).
SpecObj	Spectroscopic measurements (redshifts, classifications).
Galaxy	View of PhotoObj filtered to galaxies.
Star	View of PhotoObj filtered to stars.

Rate Limits

No formal documented rate limits. Queries returning very large result sets may time out. Use TOP N in SQL queries to limit results. For bulk data, use CasJobs (https://skyserver.sdss.org/CasJobs/) with a free account.